Process for manufacturing white leather



Patented Mar. 2 6, 1940 i UNITED STATES PATENT OFFICE PROCESS FOR MANUFACTURING WHITE LEATHER August 0. Orthmann, Milwaukee, Wis., and Fred C. Wright, Glen Ellyn, Ill., assignors to R. T. Vanderbilt Co. Inc., New York, N. Y., a cornotation of New York No Drawing. Application March 19, 1937, 1 Serial No. 131,882

6 Claims. (Cl. 1497) This invention relates generally to the manthe color of the surface of the grain side and the ufacture of leather and more particularly to a resulting leather is substantially or practically process for incorporating pigments in hides, homogenous in its pigment content. This elimiskins. or the like during the tanning thereof. nates any sharpor decided contrast between the The invention, while applicable with especial color of the body of the leather and the surface advantages to the manufacture of white leather thereof thereby making full use of the hiding by the chrome tanning process, may also be used power of the pigment and bringing about a stafor incorporating various other pigments in hides ble condition so that the leather will retain its or skins. For example, not only whites but varicolor or appearance even when rubbed or sub-.

10 ous shades of chrome yellows, chrome greens, jected to an abrading action. 10 blues and reds (iron oxides) may be used. And Generally speaking, these desirable results are the process of the-present invention may also be obtained by milling the pigment into the leather employed in connection with the egetable tan in rotating drums while the leather is in an open, ning of sheep skin, calf skin, and the like, when porous condition and when the open fibers of the tanning operation is effected by milling the the leather are pervious to rather complete pen- 5 skins in drums in the presence of a suitable tanetration by the pigment. This may be advanning liquor. tageously accomplished in the early stages of i For the sake of illustration 01' example the ineither chrome or vegetable tanning and with vention will be described in detail as applied to various pigments.

the manufacture of white leather by the chrome In chrome tanning, after the hides, skins, or 30 tanning process. the like are unhaired, they are bated and pickled Heretofore in the manufacture of leather of and then chrome tanned, that is, the hides are this character the white pigments employed have milled in suitable drums in a suitable liquor or been applied to the leather while it is being fat solution containing a basic chromium salt.

liquored or just before the fat liquoring opera- At this time the hides are, as indicated, in an 35 tion. At such time the leather is tightened up, open porous, fibrous condition. The present inthat is, is relatively impervious or non-porous vention proposes to incorporate the pigment in and, as a consequence, the added pigment has the leather during the chrome tanning and for had only a surface effect on the grain side of the this purpose the pigments are added to the an leather, the underlying body' of the leather or chrome tanning liquor at the beginning of the intermediate portion of the hide remaining dark chrome tanning operation, and are worked into in color. As a result, there is a marked or subthe leather while the hides are being milled in stantial contrast between the whitened surface the rotating drums in the presence of the chrome of the leather and the dark colored body undertanning liquor. One pigment which may be adlying such surface. The hiding power of the vantageously'employed is an oxide of titanium pigment is overtaxed and the desired color effect or a mixture of titanium dioxide and lithopone. is lacking. A true white leather is not obtained. Where such a mixture is employed one pound of And, in many instances, the whitened surface titanium dioxide to four pounds of lithopone is being constituted differently from the underlyemployed, the proportions depending on the 40 ing body of the leather is in an unstable condiopacity of the lithopone. The amount of pig- 0 tion with the consequence that the color or apment employed is from five to fifteen per cent pearance of its surface may be impaired after (by weight) to that of the pickled hid 1- the leather has been in use for a short time. though this may vary with the hides or skins to o e O t e Obj f t e Present invention is be treated. Other well-known pigments, for ex- 5 to secu e a co p e a effective pregnation ample antimonyoxide, or the so-called extended ,5

or penetration of the pigment throughout not pigments with titanium as a base may be used. only the surface but also the body of the leather The hid s are u ually milled in the drums in d to mplish this in such a way that t e the tanning liquor and pigment for from five to q y of the leather is not, in a y eight hours. The stock is then neutralized with paired. While the concentration of the pigment an lk li t th proper degree after which it is 50 y be Somewhat greater in the region of the mechanically handled, that is, taken out, piled surface at the grain side of the leather than in up nd drained. It is then wrung out and split the interior of the body thereof, there is a comand shaved, and next retanned in the same manplete and substantially uniform impregnation so ner as before but in a shorter time. No pigment that the interior is toned down to approximate. need be employed in the retannlng operation. I

If desired, it may then be bleached although the bleaching step may be omitted in many instances. Afterwards it is washed preparatory to being fat liquored. At this stage the hides are usually colored or fat liquored. In the present instance, the whiting of the hides may be toned by a suitable coloring or bleaching operation but of course the fat liquoring must be resorted to to lubricate the fibers and soften the leather.

The essential feature of the invention is the incorporation of the pigment in the hides while they are being milled in the drums during the early stages of the tanning operation and incidentally while they are in an open or pervious fibrous condition. The other steps of the process may be varied. For example, the hides may be split and shaved after pickling instead of after the chrome tanning but where they are split and shaved after pickling they are then chrome tanned and pigmented as before.

Where the process is applied to vegetable tanning, the pigments are likewise worked into the skins or hides in an early stage of the tanning operation, that is, after the skins and hides have been unhaired, bated and pickled and when they are being milled in drums in the presence of a vegetable tanning liquor. The pigment is added to the tanning liquor as before and is milled into the hides or skins while they are in an open or pervious, porous condition whereby thorough and complete penetration of the pigment throughout the skins or hides is realized.

In any event the pigment uniformly and completely penetrates the hides so that the interior thereof is whitened or so toned down as to blend in with and present no disadvantageous contrast to the whitened surface of the grain side of the leather. The hiding power of the pigment in the grain side'thus operates to best advantage and since the pigmented leather is substantially homogenous or uniform as to pigment content and color, it is structurally stable as well as fast as to color. A quality leather of desired color and of durable character is had.

After the hides, skins, or the like have been processed and treated in the manner described, the leather may be finished in accordance with any standard or suitable practice.

From the foregoing it will be understood that the present invention produces a new article of manufacture, namely, leather having not only the surface of its grain side but also its body impregnated with pigment, with the pigment content of the surface region and of the interior of the leather practically homogenous whereby any undesirable contrast between the color of the surface and that of the interior is eliminated, the full hiding power of the surface pigment most advantageously utilized, and a surface of stable, durable structure is had.

While we have shown and described several ways in which the invention may be carried out, it is to be understood that the examples have been selected merely for the purpose of illustration and that various changes and substitution may be resorted to as will be understood by those skilled in the art without departing from the spirit of the invention or the scope of the subjoined claims.

The invention claimed is:

1. The hereindescribed process of manufacturing leather which comprises milling hides, skins, and the like in rotatable tanning drums in the presence of a tanningliquor and adding an insoluble pigment to the tanning liquor in the early stages of the tanning operation and milling the pigment into the hides while they are in an open, porous condition.

2. The hereindescribed process of manufactur ing leather which comprises milling the hides, skins, and the like in rotatable drums and in the presence of a tanning liquor after they have been unhaired, bated and pickled and adding an insoluble pigment to the tanning liquor during the milling operation and milling the pigment into the material While it is in an open, pervious and porous condition to obtain a complete and practically uniform penetration of the pigment throughout the material.

3. The hereindescribed process of manufacturing leather which comprises unhairing, hating and pickling the raw material, milling the raw material in a rotatable drum in the presence of tanning liquor containing a basic chromium salt, and adding an insoluble pigment to the tanning liquor at the beginning of the milling of the raw material and milling the pigment into the material while'it is in an open, pervious and porous condition.

.4. The hereindescribed process of manufacturing leather which comprises unhairing, bating, and pickling the raw material, milling the raw material in a rotatable drum in the presence of tanning liquor containing a basic chromium salt, and adding an insoluble white pigment containing an oxide of titanium to the tanning liquor during the milling of the material in the drum and milling the pigment into the material during the milling operation and causing it to uniformly penetrate the surface and body thereof.

5. The hereindescribed process of manufacturing leather which comprises unhairing, bating and pickling the raw material, milling the raw material in a rotatable drum in the presence of tanning liquor containing a basic chromium salt, and adding an insoluble pigment consisting of a mixture of titanium oxide and lithopone to the tanning liquor during the milling operation and milling the pigment into the material and causing it to uniformly impregnate the surface and body thereof.

6. The hereindescribed process of manufacturing leather which comprises milling. the hides, skins, and the like in rotatable drums and in the presence of a tanning liquor after they have been unhaired, bated and pickled and adding an insoluble pigment to the tanning liquor during the milling operation and milling the pigment into the material while it is in an open, pervious and porous condition to obtain a complete and practically uniform penetration of the pigment throughout the material, neutralizing and then mechanically handling the stock, split and shaving the same, retanning and then fat liquoring the stock, and finishing the leather as desired.

AUGUST C. ORTHMANN. FRED C. WRIGHT, 

